1. Field of the Invention
This invention relates to an electric-power generating apparatus for an automotive vehicle with a hybrid drive.
2. Description of the Related Art
A typical automotive vehicle with a hybrid drive includes an electric generator/motor which can be operated in either a generator mode or a motor mode. It is known to control the generation of power by the generator/motor in response to the amount of electric power remaining in a vehicle battery or the state of charge of the vehicle battery. This control reduces the power generation efficiency when power is generated at a small rate. The reduction in the power generation efficiency causes a decrease in fuel economy regarding a vehicle engine. The reduction in the power generation efficiency results from core loss (iron loss) substantially uniquely determined by the rotational speed of the shaft of the generator/motor independent of the power generating torque.
U.S. Pat. No. 5,327,992 corresponding to Japanese patent application publication number 6-48222 discloses a method for controlling a hybrid drive consisting of an internal combustion engine and at least one electric motor which can be driven via an electrical energy source. The electric motor can be operated as a generator when required. In order to reduce the fuel consumption and the emission of noxious substances of the internal combustion engine in those operating ranges in which the torque to be output by the internal combustion engine to overcome the instantaneous tractive resistances lies below a torque corresponding to ideal operation of the internal combustion engine with respect to efficiency and/or exhaust gas behavior, the internal combustion engine is operated essentially with the torque corresponding to ideal operation. The differential torque between the torque corresponding to ideal operation and the torque to be output by the internal combustion engine to overcome the instantaneous tractive resistances is used to drive the electric motor which is switched as a generator. The amount of torque taken up by the electric motor operating as a generator is controlled to a set value corresponding to the differential torque.
U.S. Pat. No. 5,336,932 corresponding to Japanese patent application publication number 6-505619 discloses a method for controlling a generator associated with an internal combustion engine of a motor vehicle such that the generator is connected to provide electricity only under specific operating conditions. The method includes the following steps: (1) inputting engine consumption characteristic map values for various engine operating parameters to a logic module; (2) determining an operating point of the engine as defined by the operating map; (3) determining whether or not the operating point is less than or equal to a predetermined value; (4) connecting the generator to a load circuit associated with the motor vehicle if the operating point is at or falls below the predetermined value; and (5) disconnecting the generator from the load circuit if the operating point is greater than the predetermined value.
It is an object of this invention to provide an electric-power generating apparatus for an automotive vehicle with a hybrid drive which has a high power generation efficiency.
A first aspect of this invention provides an electric-power generating apparatus for an automotive vehicle with a hybrid drive including a prime mover. The apparatus comprises an electric device operating as either a generator or a motor, and being connected with the prime mover for transmitting and receiving torque to and from the prime mover; means for determining a required power generation quantity; and a control unit for, in cases where the electric device is required to operate as the generator, alternately setting a power-generation execution term and a power-generation suspension term and thereby controlling the electric device to intermittently operate as the generator so as to substantially equalize a mean quantity of actual power generation by the electric device to the required power generation quantity, wherein during the power-generation execution term, the electric device operates as the generator and provides a power generation quantity greater than the mean quantity, and during the power-generation suspension term, operation of the electric device as the generator is suspended.
A second aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus wherein the control unit comprises means for setting the electric device to a highly efficient state during the power-generation execution term, and means for adjusting a ratio between the power-generation execution term and the power-generation suspension term so as to substantially equalize the mean quantity of actual power generation to the required power generation quantity.
A third aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus wherein a sum of the power-generation execution term and the power-generation suspension term is equal to 1 second or shorter.
A fourth aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus wherein the control unit comprises means for changing a torque of the prime mover in response to which of the power-generation execution term and the power-generation suspension term is currently set.
A fifth aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus further comprising means for gradually varying a command torque of the electric device.
A sixth aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus wherein the prime mover and the electric device are connected via a transmission to vehicle wheels, and the electric device is connected with a battery, and wherein the control unit comprises means for detecting a required charge quantity of the battery and setting the detected required charge quantity as the required power generation quantity, and means for changing a gear ratio in the transmission in response to the required power generation quantity.
A seventh aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus further comprising means for detecting a rotation speed of the prime mover, means for determining whether or not the detected rotational speed of the prime mover is lower than a prescribed reference speed, and means for nullifying the power-generation suspension term to continuously set the power-generation execution term in cases where it is determined that the detected rotational speed of the prime mover is lower than the prescribed reference speed.
An eighth aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus wherein the control unit comprises means for, in cases where the electric device is required to operate as the motor, alternately setting a motor activation term and a motor deactivation term and thereby controlling the electric device to intermittently operate as the motor, wherein during the motor activation term, the electric device operates as the generator, and during the motor deactivation term, operation of the electric device as the motor is suspended.
A ninth aspect of this invention provides an electric-power generating apparatus for an automotive vehicle with a hybrid drive including a prime mover. The apparatus comprises an electric device operating as either a generator or a motor, and being connected with the prime mover for transmitting and receiving torque to and from the prime mover; first means for determining whether or not the electric device is required to operate as the generator; and second means for controlling the electric device to intermittently operate as the generator in cases where the first means determines that the electric device is required to operate as the generator.
A tenth aspect of this invention provides an electric-power generating apparatus for an automotive vehicle with a hybrid drive including a prime mover. The apparatus comprises an electric device operating as either a generator or a motor, and being connected with the prime mover for transmitting and receiving torque to and from the prime mover; first means for determining whether or not the electric device is required to operate as the motor; and second means for controlling the electric device to intermittently operate as the motor in cases where the first means determines that the electric device is required to operate as the motor.
An eleventh aspect of this invention provides an electric-power generating apparatus for an automotive vehicle with a hybrid drive including a prime mover. The apparatus comprises an electric device operating as either a generator or a motor, and being connected with the prime mover for transmitting and receiving torque to and from the prime mover; first means for determining a required power generation rate; second means for determining whether or not the electric device is required to operate as the generator; and third means for controlling the electric device to intermittently operate as the generator so as to substantially equalize a mean rate of actual power generation by the electric device to the required power generation rate in cases where the second means determines that the electric device is required to operate as the generator.
A twelfth aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus further comprising means for detecting a rotation speed of the prime mover, means for calculating a maximum power generation quantity from the detected rotational speed of the prime mover, means for determining whether or not the required power generation quantity is greater than the maximum power generation quantity, and means for, in cases where it is determined that the required power generation quantity is greater than the maximum power generation quantity, correcting and equalizing the required power generation quantity to the maximum power generation quantity.
A thirteenth aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus further comprising means for detecting a rotation speed of the prime mover, means for deciding a prime-mover torque up quantity in response to the required power generation quantity, means for determining whether or not the prime-mover torque up quantity can be provided at a current value of the detected rotational speed of the prime mover, and means for, in cases where it is determined that the prime-mover torque up quantity can not be provided, updating the required power generation quantity in response to the prime-mover torque up quantity and the current value of the detected rotational speed of the prime mover.
A fourteenth aspect of this invention is based on the first aspect thereof, and provides an electric-power generating apparatus further comprising means for, in cases where the electric device is operating as the generator, comparing a generator mean torque command value and a highly efficient operation point torque of the generator to select the greater of the generator mean torque command value and the highly efficient operation point torque of the generator, and means for controlling the generator in response to the greater of the generator mean torque command value and the highly efficient operation point torque of the generator.